structure is often not that difficult because the straw is still fairly stiff at this initial stage of the process.
And yet other systems
Other companies dip the straw bales and loosen them immediately afterwards before placing the straw on an aerated floor using a loader or bun- ker filler. Using loaders to pile the straw on an aerated floor is not advisable, however, as this does not lead to a homogeneous filling process. Using a bunker filler is preferable. This will deposit the straw more gently on the aerated floor, so the mass is airier, which naturally pro- motes easier and more homogeneous aeration. Temperature and oxygen sensors are then used to check the pre-wet process and regulate by aerating. During pre-wet, it is important to prevent the straw temperature exceeding 60 degrees, otherwise too much carbon will be burnt. This can be prevented by aerating enough in time.
In this system, it is also a good idea to remove the straw from the aerated floor after a day or two, then refill it for more homogeneity. During refilling, extra water can be added if necessary. Taking this approach means that no extreme amounts of water have to be applied the first time the mixture is filled. This benefits good air flow movement through the mixture. In this process too, it only takes a few days before the straw is sufficiently soft (but not too soft). Some composters loosen the straw bales and then place the straw in a water bath using a loa- der. The loader then immerses the straw in the water. After dipping the straw is loaded onto a floor, which is often not aerated. The tempera- ture of the straw will certainly increase without aeration, but in my view, this is a far from ideal situation as it encourages the formation of anaerobic patches and excessively high straw temperatures, plus too many internal tempera- ture differences.
Yet another method uses overhead water sprinklers to wet the straw from above. These piles of straw are then ‘mixed’ by a loader every day or every two days. All too often, however, large parts of the pile are not properly mixed at all, but simply moved around. This is often done on non-aerated floors. This system is highly unadvisable due to the extreme lack of homo- geneity, and it takes up a lot of time and space. And, at the end of the pre-wet process in similar systems, I see too large differences in the end result, and during the process too many anaerobic patches.
High capacity
The straw bales can also be loosened via a straw line and wet evenly before being placed in a
bunker or on an aerated floor. This system offers high capacity and reasonable homogeneity. Dry straw bales are placed on the straw line. The baler twine is then removed automatically, and the bales are loosened using prongs and sprayed with goody water. This automatic system is often used on large compost companies. But here too, it's important to place the wet straw on an aerated floor or in a bunker. The wet straw is then removed from the bunker the next day, so it can benefit from another mix and avoid too much water being given the first time it is filled. During the first night in the bunker, the straw temperature will increase significantly, which softens the straw so that the next day water will be absorbed more easily by the straw when it is filled into another bunker.
There are also composters who apply water abundantly during pre-wetting, but this encou- rages anaerobic patches, even if the wet straw is placed on an aerated floor. The ideal situation is to get just enough water in the straw so that bacteria can start working on breaking down the hard, waxy layer. If the straw is not too wet, aeration through the straw is easier and more uniform. This straw must also be removed from the bunker in question the next day and replaced in the same or another bunker (aerated floor) and, if necessary, water should be applied. During the night after the wet straw has been filled in the bunker for the first time, the straw temperature will rise. This softens the straw structure and causes the volume to shrink hea- vily. When a new batch of fresh straw is filled in the bunker for the first time, there is not always enough space to hold all the hard, wet straw in the batch, so more straw has to be added during filling (after emptying) the day after. This might sound less homogeneous. However, in practice it shouldn't be a problem, provided the fresh straw is mixed evenly through the entire batch on the second day.
A totally different pre-wet system is a vacuum, high pressure water system, which injects water into compacted straw bales under high pressure after all the air has been sucked form the bales under negative pressure. This system appears to be too expensive compared with other well-functioning systems, and the capacity is too limited.
An important detail is to know precisely how much straw is used per batch to make the most accurate cold start calculation.
And finally, and this is not a detail but an indisputable fact, good quality compost is not only dependant on the system or a good or less good installation, but first and foremost on the knowledge, skill and experience of the compost manager responsible for production.
MUSHROOM BUSINESS 17
Putting wet, badly mixed straw on non-
aerated floors is highly
unadvisable.
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